The present invention relates to a corona charger and, more particularly, to a corona charger of the scorotron type having a corona wire and a control grid.
In a corona charger of the scorotron type, it is possible to control the maximum amount of electrification by adjusting a voltage applied to a control grid. In an electrophotographic machine, a corona charger of the scorotron type is widely used for uniformly charging a photosensitive member prior to the formation of an electrostatic latent image, and for uniformly charging the rear surface of a record paper prior to the transfer of a toner image to the record paper. In a known corona charger of the scorotron type, the corona wire for generating a corona discharge is directly secured to a base frame to which is also fixed a control grid. Therefore, it is quite difficult to replace the corona wire and control grid by new ones and to clean them. For instance, if one wishes to clean the corona wire, he must first remove the control grid from the base frame and this operation requires great care and a long time, because usually the control grid is very thin and can easily be broken. Moreover, since the corona wire and the control grid are secured to the common base frame, if the thermal expansion of the base frame, corona wire and control grid are different from each other, the corona wire and/or control grid might become loose or cut, and the desired charging function could no longer be effected.